Construction method for double-shell tank

ABSTRACT

The construction method for a double-shell tank that includes a support metallic member embedded in an outer tank side wall and a metal roof supported by the support metallic member, comprising: the outer tank side wall formation step for forming the outer tank side wall by installing concrete so that an upper surface of the outer tank side wall is a water guide surface that descends toward an outside of an outer tank; and a metal roof formation step for forming the metal roof connected to the support metallic member.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of International Application No. PCT/JP2017/000592, filed Jan. 11, 2017, which claims priority to Japanese Patent Application No. 2016-007722, filed Jan. 19, 2016. The contents of these applications are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a construction method for a double-shell tank.

BACKGROUND

For example, as shown in Patent Document 1, in order to store liquefied natural gas (LNG), a double-shell tank including an outer tank mainly made of concrete and a metallic inner tank disposed inside the outer tank is mainly used. Such a technique is disclosed in Patent Documents 2 to 4 as well.

DOCUMENTS OF THE RELATED ART Patent Document [Patent Document 1]

Japanese Unexamined Patent Application, First Publication No. 2005-247324

[Patent Document 2]

Japanese Unexamined Patent Application, First Publication No. 2003-292091

[Patent Document 3]

Japanese Unexamined Utility Model Application, First Publication No. S55-041653

[Patent Document 4]

Japanese Unexamined Utility Model Application, First Publication No. H03-084557

SUMMARY

In the case of constructing the above-described double-shell tank, a bottom cold insulating layer or the like which supports the inner tank is formed inside the outer tank. In order to maintain a cold insulation function, the bottom cold insulating layer needs to be prevented from becoming wet due to rainwater. For this reason, when the double-shell tank is constructed, a part of an outer tank ceiling is formed in advance to prevent entering of rainwater into the outer tank and then the bottom cold insulating layer is formed. More specifically, an outer tank side wall having a support metallic member embedded in its top is formed and then a part of the outer tank ceiling is formed in advance by lifting up a metal roof serving as a skeleton portion of the outer tank ceiling by air raising or the like and fixing the metal roof to the support metallic member.

However, the top of the outer tank side wall is exposed for several months until concrete is installed above the metal roof serving as the skeleton portion of the outer tank ceiling. For this reason, rainwater enters at a boundary between a concrete portion of the outer tank side wall and the embedded support metallic member and intrudes to an inner surface of the outer tank side wall in some cases. In this case, it is necessary to separately perform countermeasures or the like to prevent the bottom cold insulating layer or the like from getting wet, which causes prolonging or the like of construction or the like.

The present disclosure was made in view of the above-described problems, and an object thereof is to provide a construction method for a double-shell tank that includes an outer tank made of concrete for the purpose of preventing rainwater from intruding to an inner surface of an outer tank side wall before concrete is installed above a metal roof serving as a skeleton portion of an outer tank.

The present disclosure employs the following constitution as a means for solving the above-described problems.

The present disclosure is a construction method for a double-shell tank that includes a support metallic member embedded in an inner surface of an outer tank side wall made of concrete in a state where a part of the support metallic member is exposed and a metal roof supported by the support metallic member and forming a lower layer of an outer tank ceiling, the construction method for a double-shell tank including: an outer tank side wall formation step for forming the outer tank side wall by installing concrete so that an upper surface of the outer tank side wall is a water guide surface that descends toward an outside of an outer tank in a state where the outer tank side wall takes the support metallic member therein; and a metal roof formation step for forming the metal roof connected to the support metallic member.

According to the present disclosure, an upper surface of an outer tank side wall is a water guide surface which descends toward an outside of an outer tank. For this reason, rainwater pouring down on an upper surface of the outer tank side wall is drained from the outer tank side wall toward the outside of the outer tank side wall along a water guide surface. For this reason, a large amount of rainwater does not accumulate on the upper surface of the outer tank side wall and rainwater can be prevented from entering at a boundary between a support metallic member embedded in the outer tank side wall and a concrete portion near the support metallic member. Therefore, according to the present disclosure, rainwater can be prevented from intruding to an inner surface of an outer tank side wall before concrete is installed above a metal roof serving as a skeleton portion of an outer tank through a construction method for a double-shell tank including an outer tank made of concrete.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view showing a schematic constitution of a double-shell tank constructed by a construction method for the double-shell tank according to an embodiment of the present disclosure.

FIG. 2 is an enlarged view of a region A in FIG. 1.

FIG. 3 is a schematic diagram for explaining steps of a construction method for the double-shell tank according to the embodiment of the present disclosure, showing a state where reinforcing bars are assembled therein.

FIG. 4 is a schematic diagram for explaining steps of the construction method for the double-shell tank according to the embodiment of the present disclosure, showing a state where an inner frame and an outer frame are installed.

FIG. 5 is a schematic diagram for explaining steps of the construction method for the double-shell tank according to the embodiment of the present disclosure, showing a state where concrete is installed between an inner frame and an outer frame.

FIG. 6 is a schematic diagram for explaining steps of the construction method for the double-shell tank according to the embodiment of the present disclosure, showing a state where a metal roof is installed.

DETAILED DESCRIPTION

An embodiment of a construction method for a double-shell tank according to the present disclosure will be described below with reference to the drawings. It should be noted that the scale of members may have been appropriately changed to make the members have recognizable sizes in the following drawings.

FIG. 1 is a longitudinal cross-sectional view showing a schematic constitution of a double-shell tank 1 constructed by the construction method for a double-shell tank in this embodiment. As shown in the drawing, the double-shell tank 1 in the embodiment is a pre-stressed concrete (PC) type tank including a basement floor slab 2, an outer tank 3, a bottom cold insulating layer 4, an inner tank 5, a side cold insulating layer 6, a suspended deck 7, hangers 8, retaining walls 9, and an upper cold insulating layer 10.

The basement floor slab 2 is a member serving as a foundation which supports the outer tank 3, the inner tank 5, or the like from below and is formed in a substantially disk shape with a larger diameter than the outer tank 3 when viewed from above. The basement floor slab 2 has a heater (not shown) installed therein and prevents cold heat of stored liquefied natural gas (LNG) from being transferred to the ground. The outer tank 3 is a container made of pre-stressed concrete and is erected on the basement floor slab 2 to cover the inner tank 5. The outer tank 3 is mainly made of concrete and includes a cylindrical outer tank side wall 3 a and an outer tank ceiling 3 b connected to an upper edge of the outer tank side wall 3 a.

FIG. 2 is a schematic enlarged cross-sectional view of a connection portion (region A in FIG. 1) between the outer tank side wall 3 a and the outer tank ceiling 3 b. As shown in the drawing, the outer tank side wall 3 a includes reinforcing bars 3 a 2 embedded in a concrete layer 3 a 1, a support metallic member 3 a 3 embedded in an inner surface of the outer tank side wall 3 a such that a part of the support metallic member is exposed, and a water cut-off member 3 a 4 disposed in a boundary between the support metallic member 3 a 3 and the concrete layer 3 a 1. It should be noted that, although not shown in FIGS. 1 and 2, a sheath pipe for applying pre-stress is also installed on the outer tank side wall 3 a.

A plurality of reinforcing bars 3 a 2 are erected from the basement floor slab 2 and are disposed over the entire region in a height direction of the outer tank side wall 3 a. The plurality of reinforcing bars 3 a 2 are strength members which support the concrete layer 3 a 1 and are skeleton portions of the outer tank side wall 3 a. The support metallic member 3 a 3 is a substantially annular member which is embedded in a top of the outer tank side wall 3 a so that an inner surface thereof is flush with an inner surface of the concrete layer 3 a 1 (that is, an inner surface of the outer tank side wall 3 a). The support metallic member 3 a 3 is partially connected to the reinforcing bars 3 a 2. The support metallic member 3 a 3 is a portion to which a metal roof 3 b 1 (which will be described later) of the outer tank ceiling 3 b is connected. The water cut-off member 3 a 4 is a member which prevents rainwater from entering at the boundary between the concrete layer 3 a 1 and the support metallic member 3 a 3 during construction of the double-shell tank 1. Examples of the water cut-off member 3 a 4 can include a water-swelling water cut-off member which swells when it absorbs water.

The outer tank ceiling 3 b includes the metal roof 3 b 1 and a concrete layer 3 b 2. The metal roof 3 b 1 is a steel framework member which forms a lower layer of the outer tank ceiling 3 b, and includes a shoulder 3 b 3 and a central portion 3 b 4 as shown in FIG. 2. The shoulder 3 b 3 is an outer circumferential edge of the metal roof 3 b 1, and is welded to the support metallic member 3 a 3. The shoulder 3 b 3 includes a lower portion 3 b 5 and an upper portion 3 b 6. The lower portion 3 b 5 is concentric with the support metallic member 3 a 3 a, has the same diameter as the support metallic member 3 a 3, and is directly joined to the support metallic member 3 a 3. The upper portion 3 b 6 is supported by the lower portion 3 b 5 from below, and protrudes further outside in a radial direction of the outer tank 3 than the lower portion 3 b 5. The central portion 3 b 4 is welded to the upper portion 3 b 6 of the shoulder 3 b 3. The concrete layer 3 b 2 is supported by the metal roof 3 b 1 from below, is connected to the concrete layer 3 a 1 of the outer tank side wall 3 a, and forms an upper layer of the outer tank ceiling 3 b.

Referring to FIG. 1 again, the bottom cold insulating layer 4 is placed on an upper surface of the basement floor slab 2 and supports the inner tank 5 from below. The bottom cold insulating layer 4 is formed in a substantially disk shape with a smaller diameter than the basement floor slab 2 and is disposed coaxially with the basement floor slab 2 when viewed from above. The bottom cold insulating layer 4 is made of, for example, perlite concrete, sand, and the like. The inner tank 5 is a metallic container placed on the bottom cold insulating layer 4 and has a bottomed cylindrical shape with its upper end being an opening end. LNG is stored inside the inner tank 5. The inner tank 5 includes an inner tank bottom 5 a and an inner tank side wall 5 b erected on an edge of the inner tank bottom 5 a.

The side cold insulating layer 6 is disposed between the outer tank side wall 3 a and the inner tank side wall 5 b and is formed from granular perlite filled therebetween. Furthermore, as shown in FIG. 1, the side cold insulating layer 6 is formed up to an upper portion of the inner tank 5 and is disposed such that a portion up to an upper portion of an outer circumferential portion of the suspended deck 7 is filled with granular perlite through the retaining wall 9 formed on an upper portion of the suspended deck 7 and supporting the side cold insulating layer 6 from a side thereof.

The suspended deck 7 is a disk-shaped metallic member which is suspended and supported by the hangers 8 to block an upper end of the inner tank 5 which is an opening end from above. Each of the hangers 8 has an upper end fixed to the outer tank ceiling 3 b and a lower end fixed to the suspended deck 7. As shown in FIG. 1, the hangers 8 are disposed between the outer tank ceilings 3 b and the suspended deck 7 and suspend and support the suspended deck 7.

The retaining wall 9 is disposed in a substantially cylindrical shape along an outer edge of the suspended deck 7 and is formed from the outer tank ceiling 3 b to the suspended deck 7. The retaining wall 9 prevents the side cold insulating layer 6 made of granular perlite from entering above the suspended deck 7 (inside the tank). The upper cold insulating layer 10 is placed on an upper surface of the suspended deck 7 and is disposed inside the retaining wall 9. The upper cold insulating layer 10 is formed of a polyurethane foam or the like.

Subsequently, the construction method for the double-shell tank 1 according to the embodiment will be described with reference to FIGS. 3 to 6. It should be noted that, in the following description, it is assumed that the basement floor slab 2 has already been formed.

First, as shown in FIG. 3, the reinforcing bars 3 a 2 are assembled and the support metallic member 3 a 3 to which the water cut-off member 3 a 4 is adhered is attached to one of the assembled reinforcing bars 3 a 2. Subsequently, as shown in FIG. 4, an outer frame K1 and an inner frame K2 are installed to sandwich the assembled reinforcing bars 3 a 2. In other words, the outer frame K1 is disposed on an outer side of a formation region of the outer tank side wall 3 a and the inner frame K2 is disposed on an inner side of the formation region of the outer tank side wall 3 a. Here, the inner frame K2 is disposed to be in contact with the support metallic member 3 a 3 from an inner side of an outer tank formation side region, and a height of the inner frame K2 is set such that an upper end of the inner frame K2 and a top of the support metallic member 3 a 3 are at the same position. Furthermore, a height of the outer frame K1 is set such that an upper end of the outer frame K1 is lower than an upper end of the inner frame K2.

Subsequently, as shown in FIG. 5, concrete is installed between the outer frame K1 and the inner frame K2. At this time, a water guide surface 3 a 5 formed as an inclined surface is formed on an upper surface of a portion made of concrete installed such that the concrete connects an upper end of the inner frame K2 (that is, a top of the support metallic member 3 a 3) and an upper end of the outer frame K1. The water guide surface 3 a 5 is the inclined surface which descends toward an outside in a radial direction of the outer tank side wall 3 a.

Through the steps shown in FIGS. 3 to 5, the outer tank side wall 3 a having an upper surface which is the inclined surface formed as the water guide surface 3 a 5 is formed in a state where the outer tank side wall 3 a takes the support metallic member 3 a 3 therein. In other words, the steps shown in FIGS. 3 to 5 correspond to an outer tank side wall formation step in the present disclosure.

Subsequently, as shown in FIG. 6, the outer frame K1 and the inner frame K2 are removed and the metal roof 3 b 1 is connected to the support metallic member 3 a 3. Here, first, the shoulder 3 b 3 of the metal roof 3 b 1 is welded to the support metallic member 3 a 3. In addition, the central portion 3 b 4 of the metal roof 3 b 1 is formed on an inside of the outer tank side wall 3 a and the formed central portion 3 b 4 is lifted up and welded to the shoulder 3 b 3. Through the step shown in FIG. 6, the metal roof 3 b 1 is connected to the support metallic member 3 a 3. In other words, the step shown in FIG. 6 corresponds to a metal roof formation step in the present disclosure.

As shown in FIG. 6, when the metal roof 3 b 1 is connected to the support metallic member 3 a 3, a space surrounded by the outer tank side wall 3 a is covered with the metal roof 3 b 1. In this way, the bottom cold insulating layer 4, the inner tank 5, the side cold insulating layer 6, the suspended deck 7, the hangers 8, the retaining wall 9, and the upper cold insulating layer 10 are formed in the space covered with the metal roof 3 b 1. Concrete is installed on an upper portion of the metal roof 3 b 1 after or in parallel with the work in the space covered with the metal roof 3 b 1 and thus the concrete layer 3 b 2 of the outer tank ceiling 3 b is formed. The double-shell tank 1 is completed by performing pipe installation work or the like in addition to the above steps.

Here, according to the construction method for the double-shell tank 1 in the embodiment, an upper surface of the outer tank side wall 3 a is the water guide surface 3 a 5 which descends toward the outside in the radial direction of the outer tank 3 until the concrete layer 3 b 2 is formed above the metal roof 3 b 1. Rainwater pouring down on the upper surface of the outer tank side wall 3 a drains from the outer tank side wall 3 a toward the outside of the outer tank side wall 3 a along the water guide surface 3 a 5. For this reason, a large amount of rainwater does not accumulate on the upper surface of the outer tank side wall 3 a and rainwater can be prevented from entering at a boundary between the support metallic member 3 a 3 embedded in the outer tank side wall 3 a and the concrete layer 3 a 1 near the support metallic member 3 a 3. Therefore, according to the double-shell tank 1 in the embodiment, rainwater can be prevented from intruding to an inner surface of the outer tank side wall 3 a before concrete is installed above the metal roof 3 b 1 serving as a skeleton portion of the outer tank 3.

Also, in the construction method for the double-shell tank 1 according to the embodiment, the water guide surface 3 a 5 is formed as an inclined surface which descends toward the outside of the outer tank 3. For this reason, rainwater can be reliably guided toward the outside of the outer tank side wall 3 a in the entire region of the upper surface of the outer tank side wall 3 a. Therefore, according to the construction method for the double-shell tank 1 in the embodiment, rainwater can be more reliably prevented from entering at the boundary between the support metallic member 3 a 3 and the concrete layer 3 a 1 near the support metallic member 3 a 3.

In the construction method for the double-shell tank 1 according to the embodiment, in the outer tank side wall formation step, the inner frame K2 which is brought into contact with the support metallic member 3 a 3 from an inside of an outer tank side wall formation region and the outer frame K1 which is disposed on an outside of the outer tank side wall formation region and has an upper end lower than an upper end of the support metallic member 3 a 3 are positioned and concrete is installed between the outer frame K1 and the inner frame K2. For this reason, since the upper end of the support metallic member 3 a 3 and the upper end of the outer frame K1 are used as references and an inclined surface connecting these upper ends is formed, the water guide surface 3 a 5 can be easily formed. Therefore, the water guide surface 3 a 5 with a uniform inclination can be formed over the entire circumference of the outer tank side wall 3 a.

In the construction method for the double-shell tank 1 according to the embodiment, in the outer tank side wall formation step, concrete is installed after the water cut-off member 3 a 4 is adhered to the support metallic member 3 a 3. For this reason, the water cut-off member 3 a 4 can be easily disposed in the boundary between the support metallic member 3 a 3 and the concrete layer 3 a 1. Since the water cut-off member 3 a 4 is provided, rainwater can be prevented from intruding to the inner surface of the outer tank side wall 3 a even when rainwater enters at the boundary between the support metallic member 3 a 3 and the concrete layer 3 a 1 near the support metallic member 3 a 3.

Also, in the construction method for the double-shell tank 1 according to the embodiment, the upper portion 3 b 6 of the shoulder 3 b 3 in the metal roof 3 b 1 protrudes outward from the lower portion 3 b 5. For this reason, rainwater falling on the metal roof 3 b 1 can be prevented from falling to the vicinity of the support metallic member 3 a 3 along the lower portion 3 b 5. Therefore, rainwater can be more reliably prevented from entering at the boundary between the support metallic member 3 a 3 and the concrete layer 3 a 1 near the support metallic member 3 a 3.

While the preferred embodiments of the present disclosure have been described above with reference to the drawings, the present disclosure is not limited to the above-described embodiments. The shapes, combinations, or the like of the constituent elements shown in the above-described embodiments are merely examples and various modifications are possible on the basis of design requirements or the like without departing from the gist of the present disclosure.

For example, a constitution in which the water guide surface 3 a 5 is an inclined surface has been described in the above-described embodiments. However, the present disclosure is not limited thereto and a constitution in which the water guide surface 3 a 5 is a stepped surface which gradually descends toward the outside of the outer tank side wall 3 a can also be adopted. It is possible to prevent rainwater falling on a region of the upper surface in the outer tank side wall 3 a close to the outer side from flowing in a direction toward the support metallic member 3 a 3 disposed close to the inner side, and It is possible to prevent rainwater from entering at the boundary between the support metallic member 3 a 3 and the concrete layer 3 a 1 near the support metallic member 3 a 3 even when such a constitution is adopted. Furthermore, a constitution in which the water guide surface 3 a 5 is configured to have a shape obtained by combining an inclined surface, a stepped surface, and the like can also be adopted.

A constitution in which a guide groove is formed in the water guide surface 3 a 5 can also be adopted in the above-described embodiment. When this constitution is adopted, a flow of rainwater can be more reliably guided due to the guide groove, and for example, rainwater can be intensively drained from a desired portion.

A constitution in which the water guide surface 3 a 5 is formed by disposing the outer frame K1 having the upper end lower than the upper end of the support metallic member 3 a 3 and using the upper end of the support metallic member 3 a 3 and the upper end of the outer frame K1 so as to form the inclined surface connecting these upper ends has been described in the embodiment. However, the present disclosure is not limited thereto and a constitution in which heights of the outer frame K1 and the inner frame K2 are the same and the inclined surface is formed by another method may be adopted.

Also, a constitution in which the water cut-off member 3 a 4 is adhered to the support metallic member 3 a 3 in advance before concrete is installed has been described in the embodiment. However, the present disclosure is not limited thereto and a constitution in which the water cut-off member 3 a 4 is not provided, a constitution in which the water cut-off member 3 a 4 is provided at another location after concrete is installed, and the like can also be adopted.

INDUSTRIAL APPLICABILITY

According to the present disclosure, rainwater can be prevented from intruding to an inner surface of an outer tank side wall before concrete is installed above a metal roof serving as a skeleton portion of an outer tank. 

What is claimed is:
 1. A construction method for a double-shell tank that includes a support metallic member embedded in an inner surface of an outer tank side wall made of concrete in a state where a part of the support metallic member is exposed and a metal roof supported by the support metallic member and forming a lower layer of an outer tank ceiling, the construction method for a double-shell tank comprising: an outer tank side wall formation step for forming the outer tank side wall by installing concrete so that an upper surface of the outer tank side wall is a water guide surface that descends toward an outside of an outer tank in a state where the outer tank side wall takes the support metallic member therein; and a metal roof formation step for forming the metal roof connected to the support metallic member.
 2. The construction method for a double-shell tank according to claim 1, wherein the water guide surface is an inclined surface that descends toward the outside of the outer tank.
 3. The construction method for a double-shell tank according to claim 1, wherein, in the outer tank side wall formation step, an inner frame which is brought into contact with the support metallic member from an inside of an outer tank side wall formation region and an outer frame which is disposed on an outside of the outer tank side wall formation region and has an upper end lower than an upper end of the support metallic member are positioned and concrete is installed between the inner frame and the outer frame.
 4. The construction method for a double-shell tank according to claim 2, wherein, in the outer tank side wall formation step, an inner frame which is brought into contact with the support metallic member from an inside of an outer tank side wall formation region and an outer frame which is disposed on an outside of an outer tank side wall formation region and has an upper end lower than an upper end of the support metallic member are positioned and concrete is installed between the inner frame and the outer frame.
 5. The construction method for a double-shell tank according to claim 1, wherein, in the outer tank side wall formation step, concrete is installed after a water cut-off member is adhered to the support metallic member.
 6. The construction method for a double-shell tank according to claim 2, wherein, in the outer tank side wall formation step, concrete is installed after a water cut-off member is adhered to the support metallic member.
 7. The construction method for a double-shell tank according to claim 3, wherein, in the outer tank side wall formation step, concrete is installed after a water cut-off member is adhered to the support metallic member.
 8. The construction method for a double-shell tank according to claim 4, wherein, in the outer tank side wall formation step, concrete is installed after a water cut-off member is adhered to the support metallic member. 